Method of producing a sealing deposit in a well bore



Patented Junev 19, 1945- METHOD OF PRODUCING A SEALING DEPOSIT IN A WELL BORE Leonard CQChamberIain, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich, a corporation of Michigan No Drawing.

4 Claims.

The invention relate to a method of sealing fissures, cavities and the like in earth formations,

dams, retaining walls, deep wells, such as oil and gas wells, and other similar openings. It more especially concerns a method of producing a strong solid plug or sealing deposit with a material capable of expanding while undergoing transition into a strong, solid, cohesive mass.

It oftentimes happens that, fissures, cracks, cavities, and the like in earth walls, dams, mines, etc., require sealing or plugging in order toconsolidate the structure and prevent leakage therethrough. It is highly desirable that the material employed for carrying out the sealing or plugging operation be capable of expanding after it has been placed at the desired location so that the resulting sealing deposit will be firmly held againstthe walls of the cavity, fissue, or the like, thus producing a much more effective seal resistant to dislodgment. A seal of the type described above is particularly desirable for use in wells, such as oil and gas wells, wherein it is oftentimes desirable to be able to seal off the bottom section of the well bore in order to curtail the infiltration of water, brine or other undesirable fluids into the well bore. Additionally, it is oftentimes desirable in the case of wells to be able to place a bridge or plug in the cased or uncased bore hole at a specific point in order to more closely control fluid treating agents, such asare commonly used in cementing and other work-over operations.

It is, therefore, the-principal object of the invention to provide, a method of producing a seal in a cavity or fissue occurring in an earth formation or other structure of the type wherein expansion'of the sealing material occurs during the sealing operation;

Another object of the invention'is-to a method of producing a plug or seal at any desired point in the bore of a well.

Still another object of the invention is to provide a method and material whereby cavities and fissures in earth formations, dams, and the like can bereadily sealed off with a strong, dislodgment-resisting seal.

Other objects and advantages will be apparent as the description of the invention proceeds.

According to the invention there is introduced into the fissure, cavity, well bore, or other location which is to be sealed off, a quantity of magnesium, preferably in fragmented form such as shavings, chips, powder, or other relatively finely divided particles. Thereafter a corrosive liquid capable of forming a solid, water-insoluble corrosionproduct upon reaction with the magnesium is caused to contact the magnesium. The action of the corrosive solution causes the magnesium to chemicallyreact and form a hard consolidated deposit believed to consist mainly of magnesium provide Application November 18,1942, Serial No. 466,059

hydroxide and/or magnesium oxychloride, oxysulfate, etc., depending upon the particular electrolyte used, which fills thev cavity or fissure and presses against the walls thereof. As the magnesium reacts and disintegrates upon contact with the corrosive liquid, expansion takes place due to the fact that the corrosion products of the I reaction occupy considerably more volume than the magnesium metal, and thus a highly eifective seal is produced wherein the sealing material is pressed strongly against the walls of the fissure, cavity, or well bore. The deposit is characterized by forming as a solid cohesive mass rather than as a looseunconsolidated mass, and thus a continuous fluid tight seal is produced of a highly dislodgement-resisting nature.

' In utilizing the method of the invention to produce a strongly consolidated seal in a fissure or cavity occurring in the retaining walls of a dam structure, by way of example, the following procedure is employed. A quantity of magnesium, preferably in fragmented form such as shavings, chips, powder, or similar comminuted form, is introduced into the cavity or fissure. The quantity to use depends of course upon the size and extent of the cavity. In any event, it will be usually desirable to employ an amount such' as will substantially fill the cavity or fissure. Thereafter va quantity "of a suitable corrosive liquid, such as an aqueous solution of sodium chloride, is caused to contact the magnesium. The contact between the corrosive solution and the magnesium is maintained for a suitable length of time and, if necessary, the corrosive solution may be renewed from time to time if it becomes exhausted. In any case the corrosive solution is allowed to remain in contact with the magnesium until the reaction has progressed to a point where the reaction product has. completely sealed the fissure and is pressing strongly against the surrounding walls.

Similarly in carrying out the method of the invention to produce a strong solid seal in the bottom of a well bore, the following procedure may be suitably employed. A quantity of magnesium is introduced into the bottom of the well bore in the form of shavings or the like, and preferably compressed or tamped down by allowing a cable controlled bit or other tool to drop on top of the mass ofmagnesium thus forming a semi-compact .mass of magnesium in the bottom of the well bore.

The quantity of magnesium to employ depends,

of course, on the extent of the bore to be sealed and the diameter of the bore at this point;

enough being employed to'substantially fill the hole over the extent it is desired to seal. Thereafter a quantity of a suitable corrosive liquid is caused to contact the magnesium, as byintroducing such a solution into the well bore and applying pressure thereon, if desired, to force it to the de- "resulting seal.

' to give the desired reaction product and effect a seal after a time. In any case the corrosive solution is allowed to remain in contact with the magnesium until the reaction has progressed to the point where a solid plug is formed in the bore hole. It will also be understood that the method of the invention is useful in connection with placing a seal or bridge in a well casing or a well bore at any point as by placing and maintaining the magnesium at the desired point in the well bore while contacting it with the desired corrosive solution. Additionally, pipes or similar conduits may be plugged employing the same procedure. Other uses of. the method and material include -sealing the annular space between concentric pipes, sealing a well casing in the well bore, and similar uses.

Illustrative of a length of time that has been found satisfactory for the reaction of the corrosive solution and the magnesium is from 6 hours to 3 days or more, depending on the particular corrosive solution being employed, the form and composition of the magnesium metal.

Various corrosive solutions may be employed to effect the desired decomposition of the magnesium and produce a consolidated deposit. Among those that have been found to be highly satisfactory are aqueous solutions of electrolytes such as sodium chloride, calcium chloride, sodium sulphate, magnesium sulphate, ammonium chloride, and the like. Other electrolytes may be used providing they satisfy the requirement of reacting with magnesium to produce a substantially water insoluble corrosion product. In general, the concentration of the solutions may be varied over relatively wide limits, such as from 1 to 10 per cent, although solutions having a concentration of below about'l per cent are still effective, requiring, however, an increased length of time to complete the decomposition reaction. -A generally preferred concentration is from 2 to 5 per cent.

The magnesium metal may take many forms, such as shavings, powder, rods, and the like; the fragmented forms, such as shavings and powder, having been found preferable, however. It is to be understood that the term magnesium used herein and in the appended claim is intended to include the ordinary magnesium of commerce, as well as the .well known -commercial magnesium base alloys. of magnesium alone are employed it has been founddesirable that the apparent density of the mass should not be below about 1.1 in order that the most compact and effective seal be readily produced. A mass of magnesium compacted so as to possess an apparent density of about 1.2 is generally preferred, from the point ofview of more rapid reaction, firmness, and cohesiveness of the Additionally, it hag been found that the sealing mass need not be composed entirely of magnesium. For example, a mixture of magnesium shavings with an inert filler, such In case shavings or similar forms her described above.

as lead wool, water insoluble inorganic salts, and the like, wherein the magnesium is present in an amount of at least about 25 per cent by weight also gives an effective sealing composition. In case an alloy is selected for use it will be desirable to choose one that is not extremely resistant to corrosion by the solution, such as indicated above, although the more highly corrosion resistant alloys can be used. Alloys will be generally chosen which exhibit rather rapid corro sion characteristics in the presence of the aforementioned corrosive solutions. Illustrative of alloy compositions exhibiting relatively rapid corrosion rates generally suitable for use are magnesium-silver alloys containing up to about 10 per cent of silver and magnesium-silicon alloys containing up to about 5 per cent of silicon.

In the foregoing manner a highly effective seal can be produced in an open well bore, cavity in an earth formation, dam, or similar structure by placing a quantity of magnesium or an alloy thereof in such opening and causing a suitable corrosive liquid to contact the metal in the man- The use of the metal as a sealing material has the, advantage that the resultant deposit is expanded against the walls of the well bore or cavity and is held firmly thereagainst under a' relatively higher pressure, thus resisting displacement and at the same time effecting a tighter seal.

I claim:

1. In a method of producing a sealing deposit in a well bore, the steps which consist in placing a mass of magnesium in the well bore, compressing the fragmented magnesium to a compact mass and thereafter allowing a corrosive solution to contact the mass of magnesium, said solution being capable of forming a solid, water-insoluble corrosion product upon reacting with the magneslum.

2. In a method of producing a sealing deposit in the bore of a well, the steps which consist in placing amass containing about 25 per cent by weight of fragmented magnesium at the desired location in the well bore, said fragmented magnesium having a specific gravity not less than 1.1, and. thereafter allowing a corrosive solution to contact the mass of magnesium, said solution being capable of forming a solid, water-insoluble corrosion product upon reacting with the magnesium.

3. In a method of producing a sealing deposit in the bore of a well, the steps which consist in placing a quantity of fragmented magnesium in the well bore, compressing the magnesium to a compact mass and thereafter introducing into the well bore a quantity of ammonium chloride and allowing said solution to contact the magnesium for a suflicient length of time to produce a seal in the well bore. P

4. In a method of producing a sealing deposit in the bore of a well producing brine, the steps which comprise introducing a mass of fragmented magnesium into the well bore at the location to be sealed, compressing the magnesium to a compact mass, and thereafter allowing said brine to remain in contact with the magnesium for sumcient length of time toproduce a sealing deposit in the bore hole. 

